Electronic fuel injection system

ABSTRACT

An electronic circuit for metering solenoid fuel injectors for an automobile is controlled entirely by voltages produced by a plurality of electrical sensors of engine operating conditions. A ramp voltage generator is triggered by an engine produced pulse to generate a pair of sawtooth output voltages having equal but opposite slopes determined by the sensor outputs, and at the same time a current pulse for opening the fuel injectors is initiated. When the sawtooth voltages reach and exceed a reference level they actuate a comparator circuit, which produces an output pulse that causes a transistor circuit to terminate the current pulse and close the fuel injectors. The end of the current pulse causes the ramp voltage generator and the comparator circuit to be reset to their initial conditions.

' United States Patent [19-1 Beishir [451 Jan; 16, 1973 [54] ELECTRONIC FUEL INJECTION SYSTEM [75] Inventor: I Richard Bert Beishir, St. Louis, Mo.

[73] Assignee: ACF Industries, Incorporated, New

York, NY.

22 Filed: May 14, 1970 21 App1.No.:37,094'

UNITED STATES PATENTS FOREIGN PATENTS OR APPLICATIONS Primary ExaminerLaurence M. Goodridge Assistant Examiner-Cort Flint Attorney-Edward H. Casey [57] ABSTRACT An electronic circuit for metering solenoid fuelinjectors for an automobile is controlled entirely by voltages produced by a plurality of electrical sensors of engine operating conditions. A ramp voltage generator is triggered by an engine produced pulse to generate a pair of sawtooth output voltages having equal but opposite slopes determined by the sensor outputs, and at the same time a current pulse for opening the fuel injectors is initiated. When the sawtooth voltages reach 3,464,396 10/1969 Scholl ..123/32 EA a 3 338 22 8,1967 Scholl 23/32 EA and exceed a reference level they actuate a compara- 3'6l2'009 10/1971 iig'i 123/H9 R tor circuit, which produces an output pulse that causes 7 2644:O94 6/1953 Douglas "12352 EA a transistor circuit to terminate the current pulse and 3,314,407 4/1967 Schneider ..123/148 E close the fuel injectors. The end of the current pulse 3,456,628 7/1969 Bassot et al. ..123/32 EA causesthe ramp voltage generator and the comparator 3.575.146 4/1971 C e ghton e 3/3 A circuit to be reset to their initial conditions. 3,548,792 12/1970 Palmer ..123/32 EA I 3,430,616 3/1969 Glockler ..l23/32 EA 5 Claims, 3 Drawing Figures 17 0 24 n M n n 231:; 11: .22:5? GEN. CI RCUIT CIRCUIT AMPL'F'ER 'NJECTORS v 2a 2a .6 .1 22 l J ENclNE FUEL RAMP DEMAND VOLTAGE Q B INFORMATION GENERATOR SENSORS J CKTT l l 14 10 l2 l3 REG.

10/1970 Germany ..123/32 EA.

SHEET 1 OF 3 PATENTEDJAH 16 I975 PATENTEDJAN 16 1973 SHEET 2 BF 3 INVENTOR. RICHARD B. BEISHIR ATTORNEY.

ELECTRONIC FUEL INJECTION SYSTEM BRIEF DESCRIPTION OF THE PRIOR ART Prior art electronic fuel injection systems typically include a monostable multi-vibrator as the timing device or circuit for controlling the quantity of fuel discharged by the fuel injection nozzles. One of the earlier examples of this type of system is Sutton et al. US. Pat. No. 2,980,090 issued Apr. 18, 1961. Systems of this type have been developed into commercial units and are very successfully operating automobiles throughout the world.

Despite the success of the aforementioned systems, there are certain unfavorable features which if improved would result in an even better system. For example, the monostable multi-vibrator relies upon a RC circuit or a LC circuit for controlling the time duration of the excursion to the unstable side. There are inherent disadvantages of this scheme in that the duration of the excursion is not always as precise as may be desired. Also, it may be noted that the inputto the system, namely the trigger, frequently experiences difficulty because of spurious trigger signals that originate from sources outside the system such as the ignition system of the vehicle or even the ignition system of the vehicle nearby on the roadway. Whenever a spurious signal is of sufficie'nt amplitude to trigger the system, there is a resultant unnecessary discharge of fuel into the intake manifold of the engine. Y

Accordingly, it is an object of the invention to provide an electronic fuel injection system which does not rely upon a monostable multi-vibrator and instead utilizes an entirely different timing concept. It is a further object of the invention to provide an electronic fuel injection system which utilizes an on-off circuit which is turned on by a trigger signal and which is turned off by a timing circuit which is separate from the on-off circuit. A further object of the invention is to provide a sample hold circuit which turns on with the initiation of a trigger pulse and which also initiates a ramp voltage generator circuit to produce a ramp voltage and the resultant ramp voltage is then passed to a comparator circuit for the creation of a pulse which turns off the sample hold circuit.

A further object of the invention is to sense engine variables which are representative of the engine fuel requirements and to utilize this information to control the operation of the ramp voltage generator so that the ramp voltage generated will be a precise measure of the quantity of fuel delivered to the engine.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing consists of the following figures: I

FIG. 1 is a block diagram of the circuit for the electronic fuel in jection system of this invention.

FIG. 2 is the electronic schematic diagram of the upper one half of the electronics of FIG. 1.

FIG. 3 is a electronic schematic diagram of the lower one halfof the electronics of FIG. I joined to FIG. 2 at terminals X-X and Y-Y.

DESCRIPTION OF THE PREFERRED EMBODIMENT suitable manifold pressure sensor is disclosed in my application Ser. No. Il,428, filed .Feb. 16, 1970. Ap-

paratus for sensing the engine operating conditions supplies the resulting D.C. voltages to ramp voltage generator 12, which produces linear sawtooth waves or ramp voltages having a slop, or rate of change, determined by the engine fuel demand voltages. The ramp voltages are impressed on comparator circuit 14 to produce a sharp reset pulse 15 when the ramp voltages reach a predetermined level, established by a biasing voltage on comparator circuit 14 derived from a +9 volt source. g

A starting pulse 17 derived from the ignition circuit or engine-driven switching means 16 is fed to differentiating circuit 18, and the resulting sharp pulse 20 is fed to a sample-hold circuit 22; The latter produces a step voltage which is terminated by output pulse 15 of the comparator 14. Hence, sample hold circuit 22 produces pulses 24 in synchronism with the engine and of a duration inaccordance with engine fuel demand. Pulses 24 are fed through power amplifier 26 to fuel injectors 28 to hold the injectors open fora desired time during each engine cycle. Injectors 28 are opened at time t, determined bythe starting pulse I'Iand closed at a time determined by the enginefuel demand information. The output of amplifier 26 is fed .to ramp voltage generator 12 via line 30. to turn it on at time t,, and to turn ramp generator 12 off at time I FIGS. 2 and 3 are diagrams of a circuit correspond- I ing to the block diagram of FIG. I. A differential amplifier having a pair of field effect transistors-31, 32 is con nected by output circuit 34 to a plus nine volt source at terminal 36. Transistors 31 and 32 have a number of positive voltage inputs 3840 and an additional number of positive voltage inputs 42-44 from sensors responsive to various engine operating and fuel demand conditions. Transistors 31 and 32 are connected to ground I ferential output amplifier. Its dual output produces linear ramp voltages of the form indicated by wave forms 56, 57. In the rest condition output terminal58is at voltage V, and terminal 59 is at voltage V When a positive going pulse is applied to the base of transistor 60, it de-energizes and allows terminal 52 to assume the voltage impressed on-it by transistor 31'. The voltage at terminals 58, 59 then change as indicated at-56, 57 for the duration of the pulse applied to the base of transistor 60. The slope or rate of change of waveforms 56, 57 are determined by the output of differential amplifier 31, 32.

same level; namely, V,+ V /2, comparator circuit 14 produces output pulses l5. Comparator 14 is a high gain differential input amplifier. Pulse 15 occurs a predetermined time after a trigger signal (described hereinafter) occurs and this timecontrols the time duration that the solenoid injector valves are open. Since the timing of pulse 15 depends on the slopes of voltages 56 and 57, which in turn depend on the output of transistors 31 and 32 in response to the fuel demand voltages on terminals 38 to 44, the solenoid valves remain openfor an interval determined by the voltages on terminals 38 to 44.

Triggering pulses 17, derived from the ignition circuit or otherwise, are impressed on terminal 74 of differentiating circuit 18 to produce differentiated pulse across inductance 80. Pulse 20 is applied to the base of transistor 82, making it conductive and thus charging capacitor 84, which holds the charge until pulse 15 is applied to the base of transistor 86, causing it to conduct and discharge capacitor 84. The resultant rectangular positive pulse applied to terminal 88 makes field effect transistor 90 conductive, causing a positive pulse developed across resistor 92 to be applied to the base of transistor 94. The latter is coupled to transistors 96 and 98. The positive voltage pulse applied to the base of transistor94 causes its output voltage, impressed on the base of transistor 96,'to drop from +12 to +11 volts and makes transistor 96 conductive, and this in turn causes the voltage on the base of transistor 98 to drop to +11 volts, thus making transistor 98 conductive. Transistor .98 is a power amplifier serving to energize the solenoids 104 of the solenoid fuel injectors, all of which may be connected in parallel. A positive voltage pulse is developed across resistor 100 and fed over line 102 to the base of transistor 60 to cut it off and thereby unclamp terminal 52, as described above. At the end of this positive pulse, determined by comparator output pulse 15, transistor becomes conductive again, clamping terminal 52 relative to ground and restoring ramp voltage generator, and consequently comparator 62, to their rest conditions. The circuit is then ready for the next energization to fuel injectors 104. What is claimed, is:

1. An electronic circuit for an automobile fuel injection system comprising a ramp voltage electronic generator for producing a pair of oppositely' and uniformly varying ramp voltages, means for varying the rate of change of said ramp'voltages in accordancewith engine fuel demand, means for producing starting pulses in accordance with engine speed, means for causing 2. Apparatus according to claiml, including means for resetting said ramp voltage generatorin response to the comparator output pulse.

3. Apparatus according to claim 1, wherein said ramp voltage generator produces a pair of oppositely varying ramp voltages, said comparator circuit producing an output pulse in response tothe relative instan taneous values of said pair of ramp voltages.

4. Apparatus according toclaim 1, wherein said.

means for varying the rate of change of said ramp voltage includes a differential amplifier for-impressing a pair of differential output voltages on said ramp voltage generator, and means for impressing on the inputs of said differential amplifier a plurality of voltages.

5. Apparatus according to claim 4, including means for stabilizing said differential amplifier against temperature changes.

i k i i 

1. An electronic circuit for an automobile fuel injection system comprising a ramp voltage electronic generator for producing a pair of oppositely and uniformly varying ramp voltages, means for varying the rate of change of said ramp voltages in accordance with engine fuel demand, means for producing starting pulses in accordance with engine speed, means for causing said ramp voltage generator to produce a ramp voltage in response to each starting pulse, circuit means for starting a rectangular pulse in response to each starting pulse, a comparator circuit for producing an output pulse in response to predetermined relative instantaneous values to said pair of ramp voltages, means for terminating said rectangular pulse in response to the comparator output pulse, a plurality of fuel injector valves, and means for feeding the rectangular pulses to said fuel injector valves.
 2. Apparatus according to claim 1, including means for resetting said ramp voltage generator in response to the comparator output pulse.
 3. Apparatus according to claim 1, wherein said ramp voltage generator produces a pair of oppositely varying ramp voltages, said comparator circuit producing an Output pulse in response to the relative instantaneous values of said pair of ramp voltages.
 4. Apparatus according to claim 1, wherein said means for varying the rate of change of said ramp voltage includes a differential amplifier for impressing a pair of differential output voltages on said ramp voltage generator, and means for impressing on the inputs of said differential amplifier a plurality of voltages.
 5. Apparatus according to claim 4, including means for stabilizing said differential amplifier against temperature changes. 